The root cause of this is likely because there is some legacy system at the bottom of the authentication stack. The password rules give this away -- there is an

The root cause of this is likely because there is some legacy system at the bottom of the authentication stack. The password rules give this away -- there is an upper limit on length (50 characters), and you can't use symbols (@, $, etc) or spaces (precluding xkcd-style "correct battery horse staple" memorable passwords). Use a password manager ("storing passwords under symmetric encryption") and don't reuse your password across sites.